Flashcards in Final Deck (79)
Clinical Electromyography (EMG)
used to evaluate the scope of neuromuscular disease or trauma as well as assist with establishing anticipated goals and expected outcomes
Forms of clinical EMG:
Nerve conduction velocity (NCV)
Electromyography (needle EMG)
used to study muscle activity and establish the role of various muscles in specific activities
Electromyography (primarily surface EMG)
describes the use of instrumentation to make covert physiological processes more apparent to the patient
Best and most widely used electrodes:
silver silver chloride
How many electrodes:
What do the 2 active electrodes do?
primarily sense the activity of the muscle
What does the isolation electrode do?
make sure the two active electrodes only pickup electricity that is coming from the patient
Where are the active electrodes placed?
both active electrodes are generally placed at the midpoint of the muscle being recorded in line with the muscle fibers
Considerations for placing electrodes:
Place electrodes in position of movement
Consider how skin may shift over the underlying muscle during movement
What does closer spacing of the electrodes give?
smaller sampling are and lower amplitude of signals
What does wider spacing of the electrodes give?
larger sampling area and higher amplitude of signals
What is volume conduction?
the salt water conducts electricity through its volume and allows us to record from the surface of the skin
What is cross talk?
when the electrodes are far apart you can get recordings from other muscles
What is an artifact?
an excess or erroneous signal that is detected and displayed but does not come from the electrical activity of motor neurons or muscle tissue
What are the different types of artifact?
power line interference
shift on the screen that is from the movement of wires not electrical activity
Power line interference:
if the reference ground isn’t on the pt and eliminating electrical interference
What happens during the processing phase?
rectification and integration
What is filtering:
generally, the electrical signal from the pt is filtered to only allow frequency components of 80-250 Hz to pass
What is rectification and integration:
so that it makes more sense for us to look at and appreciate change
we can determine how fast the display on the screen follows changes in electrical activity of muscle
Low time constant (low smoothing)
screen displays changes very quickly to follow changes in muscle activity (see moment to moment changes)
High time constant (high smoothing)
Screen display does not change quickly to follow changes in muscle activity (seeing overall effect)
Screen does not change with every step
Can be used to adjust the size of an EMG signal on a given display
some level of EMG that a pt can be prompted to contract up to or relax down to, gives the pt something to shoot for
audio feedback to patient
Types of display mode
the unit continuously displays the pts electrical activity along with any goals or other feedback